package com.gaokao.demo.filter;

import cn.hutool.core.util.StrUtil;
import com.gaokao.demo.utils.JwtTokenUtil;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.authority.SimpleGrantedAuthority;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.web.authentication.www.BasicAuthenticationFilter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;

public class JWTAuthorizationFilter extends BasicAuthenticationFilter {

  public JWTAuthorizationFilter(AuthenticationManager authenticationManager) {
    super(authenticationManager);
  }

  /**
   * 在过滤之前和之后执行的事件
   */
  @Override
  protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException {
    String tokenHeader = request.getHeader(JwtTokenUtil.TOKEN_HEADER);

    // 若请求头中没有Authorization信息 或是Authorization不以Bearer开头 则直接放行
    if (tokenHeader == null || !tokenHeader.startsWith(JwtTokenUtil.TOKEN_PREFIX))
    {
      chain.doFilter(request, response);
      return;
    }

    // 若请求头中有token 则调用下面的方法进行解析 并设置认证信息
    SecurityContextHolder.getContext().setAuthentication(getAuthentication(tokenHeader));
    super.doFilterInternal(request, response, chain);
  }

  /**
   * 从token中获取用户信息并新建一个token
   *
   * @param tokenHeader 字符串形式的Token请求头
   * @return 带用户名和密码以及权限的Authentication
   */
  private UsernamePasswordAuthenticationToken getAuthentication(String tokenHeader) {
    // 去掉前缀 获取Token字符串
    String token = tokenHeader.replace(JwtTokenUtil.TOKEN_PREFIX, "");
    // 从Token中解密获取用户名
    String username = JwtTokenUtil.getUsername(token);
    // 从Token中解密获取用户角色
    String role = JwtTokenUtil.getUserRole(token);
    // 将[ROLE_XXX,ROLE_YYY]格式的角色字符串转换为数组
    String[] roles = StrUtil.strip(role, "[]").split(", ");
    Collection<SimpleGrantedAuthority> authorities=new ArrayList<>();
    for (String s:roles)
    {
      authorities.add(new SimpleGrantedAuthority(s));
    }
    if (username != null)
    {
      return new UsernamePasswordAuthenticationToken(username, null,authorities);
    }
    return null;
  }
}
